The proposed project will study the respiratory effects of long-term, low level exposure to beryllium (Be). Workers in two beryllium processing plants have been studied over periods of several years. In the proposed project this data will be analyzed to quantify exposure-response relationships for beryllium. Data were collected on 2l4 workers (at initial survey) at one plant, and 32l at the second. These workers were surveyed over periods of eight and six years, respectively. Exposure data are available on all production jobs in both plants, and when combined with occupational histories on each subject, these data will be used to estimate current and cumulative Be exposures. Effect data available on each subject include spirometry, blood gases, chest x-rays, and respiratory symptom reports. These data will be used to study exposure-response relationships for beryllium exposure and the various measures of lung function. Because data were collected before and after "clean ups" in both plants, it will be possible to: l) study whether the disease is progressive, reversible, or stable after a drop in exposure; and 2) address the regulatory question what effect does lowering current exposure by imposition of a standard have on those who already have considerable cumulative exposure? These analyses have implications for the study of other occupational respiratory diseases in which many of the same hypotheses and data limitations arise.